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PASMA Safety (Mobile Towers)

Thanks to for the following Safety Information regarding the use of Mobile Towers.

What are the guidelines for using a mobile access tower in bad weather? 
The general guidance given by PASMA and many manufacturers is that mobile access towers (tower scaffolds) certified as conforming with the product standard EN1004 should be stable in a freestanding condition in wind speeds up to 28mph (Beaufort 6).

If the wind speed should exceed 17 mph you must STOP any work on the mobile access tower. The wind  speeds on the mobile access tower during work may be monitored using hand held anemometers which are readily available

If the wind speed is likely to reach 25 mph then the mobile access tower must be properly tied to a suitable adjacent rigid supporting structure capable of supporting the additional loads imposed by the mobile access tower. The connections (ties) between the tower and the supporting structure must be rigid in compression and tension i.e. you should NOT use rope, webbing, wire etc. You could use an arrangement of suitable aluminium or steel tubes and couplers.

As the tower must be tied if the wind speed is likely to reach 25mph, you will need to consider this point and take appropriate measures in your planning for the task. Potential wind speeds may be established by reference to weather forecasts for the duration of the time that the mobile access tower will be standing and also by reference to metrological data for the geographical area where it will be located.

If the wind speed is likely to reach 40mph, then the mobile access tower must be dismantled. Again, you will need to consider this point and take appropriate measures in your planning for the task.

The location of the site and the surrounding terrain will affect potential wind speeds e.g. on the top of a slope, hill, escarpment or cliff, close to the sea or estuaries, near woodland, in open country or near buildings. All of these terrains have an effect on wind speeds.

If the mobile access tower is to be placed on a high structure where it will be exposed to wind (e.g. on a tall building) then wind speeds at the top of that structure may be considerably higher compared to those experienced at ground level.

Therefore you must consider wind speed data which takes this point into account.

Where can you get information regarding good practice when using mobile towers?
The PASMA Code of Practice is the definitive stand alone reference document for good practice in the use of mobile access towers.  It is available from the PASMA online shop or you can view a copy free on the PASMA App.

Do you need the manufacturer’s instruction manual to assemble a tower?
Quite simply – if you don’t have a copy of the manufacturer’s instructions, you cannot assemble the tower.  You can find PASMA registered manufacturers instruction manuals either on their websites or on the PASMA website.

If you hire a tower you should be issued a copy by the hire company.  When you are assembling, altering or dismantling a mobile tower:

  • You must have a copy of the correct instructions with you.
  • You must note all of the safety information, the schedule of components and follow the step by step instructions every time and you must do this even if you are a PASMA trained operative.
  • Remember your PASMA training – no instruction manual means you cannot assemble the tower!

Do you need to fit stabilisers on mobile towers at 2.5m height or less?
It depends on the manufacturer’s instructions for the tower height you are building. The old 3:1 rule for the ratio of tower height to base dimension no longer works for determining the stability of a mobile tower. The base dimensions are now determined by a complex calculation in EN1004 which takes into account lots of factors. The only way you can determine if the stabilisers are required and which size of stabilisers to use, is to look it up in the manufacturer’s instructions schedule of components. Remember that you must fit stabilisers at the first opportunity in the build sequence and remove them at the end when dismantling.

Do you need to be competent to use a mobile tower to work?
There is a specific PASMA training course available for persons who will only be working from mobile towers but who are not building or dismantling, adjusting or moving them.

The Work at Height Regulations requires all persons working at height to be competent using the relevant equipment and they must be able to prove their competency.  At NTSS we offer a comprehensive Working at Height course.

When should mobile towers be inspected?
Towers must be inspected as often as is necessary to ensure safety.

PASMA recommends that on towers where it is possible to fall 2m or more you should carry out inspections after assembly or significant alteration, before use and following any event likely to have affected the towers stability or structural integrity.  You should complete and issue the inspection report in accordance with the requirements of the work at Height Regulations. Re-inspect the tower as often as is necessary to ensure safety but at least every 7 days and issue a new report each time.

You do not need to re-inspect the tower if it is moved unless it was necessary to significantly alter it to make that movement or if anything happens when moving it that may have affected its safety.

A tower from which it is possible to fall a distance of less than 2m has different inspection requirements. It must be inspected after assembly, and before use; after any event likely to have affected its stability or structural integrity and at suitable intervals depending on frequency and conditions of use.

PASMA recommends the use of the PASMA Tower Inspection Record which not only gives a visual indicator of the tower’s inspection status but also, when affixed to the tower and retained on completion, satisfies the inspection requirements of the Work at Height Regulations  PASMA has produced a pocket card and posters explaining the inspection requirements for mobile towers.  The Inspection Records, pocket card and poster may be purchased on the PASMA online shop .

Should you use a safety harness and lanyard as fall protection when working on a mobile tower?
Both PASMA and the HSE specifically recommend that you do not use a safety harness and lanyard when working on mobile towers. If the guardrails have been correctly installed then the tower has collective fall protection so personal fall protection is not necessary.

In the event of a arrested fall on a mobile tower you are likely to cause the tower to overturn increasing the risk of injury to yourself and also to others in the vicinity.

If the tower is not high enough to complete the task is it acceptable to increase the height using the adjustable legs?
Never use the adjustable legs on a mobile tower to gain extra height. The only purpose of the adjustable legs is to level the tower on uneven or sloping surfaces. At least one adjustable leg should always be on minimum extension.

Is it acceptable to use a mobile tower without the castors or base plates or adjustable legs?
Never use a mobile tower without either the castors or base plates fitted at the base of all the uprights. Never use a tower with the base of the end frames resting on the ground, even if you have placed boards or other packing beneath. They are not designed to be used in this way.

What should you do if you do need additional height or if you need to reduce the height?
They only way to increase or decrease the height of a mobile tower is to use the correct height of end frames.

Is it acceptable to assemble a mobile tower on a slope?
That depends on lots of factors so it is not possible to give an absolute answer.  Conditions on site can vary so much and only your risk assessment can determine if it is safe to assemble a tower on a slope.

It is safer to assemble a tower on a slope on base plates instead of castors. Even if the tower is on base plates you may still need to tie the tower to a supporting structure or ground anchors to prevent movement. If the slope is steep then you may need to consider digging it out locally to accommodate the base plates on a flat area.

Check if the ground surface is suitable. Loose, soft or otherwise unstable sloping ground surfaces can be particularly dangerous.  Where levelling is required beyond the adjustment available from the adjustable legs, consideration should be given to offsetting or using different end frames.

Is it acceptable to climb up the outside of the tower to get to the platform?
Never climb the outside of a tower. It is not designed to be climbed in this way and it will probably overturn on top of you! Neither should you ever lean a ladder against the tower to climb up to the platform. The only way to climb or descend a mobile tower is to use the access that is provided and built-in, which means you will always be climbing inside the tower.

The access may be provided in 3 ways:

  • Climbing end frames with a horizontal distance of 300mm or less- they must always be climbed in the inside.
  • Clip in vertical or inclined ladders – they clip on to the end frames of the tower on the inside.
  • Stairway or stair ladders – they are used where there is a need to carry tools and materials up and down.
  • Should you use the smallest end frames at the top or bottom of a mobile tower?
    If you are building a mobile tower using the 3T method, always use the smallest frames at the base e.g. start the tower with 2 rung frames at the base followed by 3 rungs frames and then 4 rung frames on top. This will allow you build the tower safely using the 3T method ensuring that the guardrails may be fitted at the correct heights through the build.

What rescue plans are there for towers?
Following investigation by PASMA, it was found that because there are so many variations in the circumstances that may be encountered when using mobile towers, it is not possible to give any specific guidance regarding rescue plans. These variations include; the reason for the rescue, the persons involved, the dimensions of the tower and its design, the state of build – either partial or complete, the location, the environmental conditions at the time, other local circumstances. All of these factors and more, create significant differences to the potential methods of rescue. However, you might consider a general hierarchy of measures for rescue from a tower which will apply in many cases.

  • Self-help comes first i.e. the person or persons are capable of descending the tower without outside assistance.
  • Next is an assisted descent i.e. the person or persons are capable of descending the tower with the assistance of others.
  • Last is professional rescue i.e. the person or persons are totally incapacitated and incapable of descending the tower and need to be removed from the tower by others. If the person or persons are incapacitated such that they are unable to descend the tower even with the assistance of others, then their condition is likely to be such that only the professional medical or rescue services (ambulance and/or fire service) would have sufficient knowledge and skills to effect a safe and successful rescue. It is highly likely that in such circumstance, persons without such professional medical and rescue knowledge and skills, could potentially cause further injury and/or significant risk to themselves or the person or persons in need of rescue.

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